Solid state image sensor having planarized structure under light shielding metal layer

Abstract

Shift register electrodes are formed in an imaging area and a peripheral area through use of a single layer of conductive film, and a thick insulating film is deposited over those electrodes and planarized. The thick insulating film overlying the shift register electrodes in the peripheral area is kept as it is and on the other hand, the thick insulating film overlying the shift register electrodes is etched to just fill gaps between the shift register electrodes with the film, thereby allowing a light shielding metal layer overlying the shift register electrodes in the peripheral area and insulating films sandwiched therebetween to be formed without discontinuity. Since metal interconnect lines in the peripheral area have a thick and planarized insulating film formed thereunder, parasitic capacitance between diffusion layers / electrodes and the metal interconnect lines can be reduced, leading to reduction in power consumption of image sensor.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a solid state image sensor, and particularly to a solid state image sensor having a planarized structure under a light shielding metal layer.[0003]2. Description of the Related Art[0004]A solid state image sensor having shift register electrodes formed from a single conductive film has conventionally been manufactured using the following method. FIGS. 1A-C through 4A-C are cross sectional views illustrating the solid state image sensor that has shift register electrodes formed from a single layer of conductive film and is manufactured using a conventional method, in the order of manufacturing steps, in which signs A, B, C correspond to a photoelectric conversion region, a vertical shift register region, a peripheral area, respectively (for example, refer to Japanese Patent No. 2571011). Note that process steps performed before formation of shift register electrodes are not shown in FIGS....

AI Technical Summary

Benefits of technology

[0013]An object of the present invention is to provide a solid state image sensor configured to include metal interconnect lines free from discontinuity and have improved smear characteristics.

[0017]As such, when employing the solid state image sensor according to the invention, the interlayer insulation film on the plurality of shift register electrodes in the peripheral area is formed thick between the light shielding metal layer and the plurality of shift register electrodes, and further formed to have a planarized surface. This prevents discontinuity in the light shielding metal layer overlying the plurality of shift register electrodes in the peripheral area and reduces power consumption of the image sensor. Furthermore, since the interlayer insulation film on the photoelectric conversion elements is formed lower than the shift register electrode adjacent the photoelectric conversion element, the light shielding metal layer can be formed to completely cover the sidewalls of the shift register electrode on the side of the photoelectric conversion element and therefore, probability of light incident on the photoelectric conversion element from a direction inclined relative to the normal of the surface of the photoelectric conversion element and entering a shift register channel below the plurality of shift register electrodes can be reduced.

Problems solved by technology

However, as shown in FIGS. 4B, 4C, the solid state image sensor manufactured using the conventional method is constructed such that particularly, an extremely small spacing is created between the shift register electrodes 830 in the peripheral area after deposition of the interlayer insulation film 806, and therefore, formation of the metal interconnect lines 808 in the peripheral area potentially results in an open circuit 809 due to poor step coverage of the associated metal films over an underlying step, unfavorably causing the image sensor to have deteriorated charge transfer ability.

Moreover, when the interlayer insulation film 806 interposed between the metal interconnect lines 808 and diffusion layers, polysilicon electrodes in the peripheral area is thin, parasitic capacitance therebetween becomes large and then causes increase in power consumption of image sensor.

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